This is a good sketch, but their postures are a lot less dynamic than Fishy Sketch. But that may be 'cause I'm comparing a colored piece to a sketch. On the other hand, the kiss looks cuter here, just like the diver is cuter too. Lol. Also, I like the way the mermaid's head is angled.
In the end it's your choice, I think they're both great.
Oh yeah definitely, the possibilities with light reflection under water are endless do it PAINT IT! Sunset, romantic atmosphere!...sorry I'm getting way too carried away, but I'm sure however you paint it would look swell.